The invention relates to an electric machine comprising a first functional part having a permanently magnetic excitation system and a second functional part having a conductor system, the first functional part and the second functional part being movable relative to each other along the active area of an air gap.
This definition describes an electric machine in its broadest form, and only the indication of a permanently magnetic excitation system reveals a more specific sector in the field of electric machines. Electric machines of this type are found most often in the form of direct current motors in which permanently magnetic north poles and south poles alternate with each other at the active area and in which the functionally required magnetic return path between adjacent magnet poles is effected either by an iron back on the back or rear side of the permanent magnets facing away from the active area, or in that the permanent magnets are partial regions of a uniform magnetic body which are magnetized in different directions. The second functional part comprises the conductor system as a rule in the form of windings or coils which are associated with individual poles. For rendering the electric motor operative, the current direction in the individual windings must be reversed by a specific distance after each relative movement of the two functional parts, which can be carried out by mechanical or electronic commutation.